Pulverizing granular materials



Mardi 16 1943- T. A. SMITH ETAL PULVERIZING GRANULAR MATERIALS Filed Nov. 28, 1959 Patented Mar. 16, 1943 Trevor 'Andrew Smith Thompson, Spondon,

and Ronald Holloway A near Derby, England, assignors to Imperial Chemical Industries Lim ited, a corporation of Great Britain Application November 28,

In Great Britain November 1 Claim.

This invention relates to -the pulverizing of 1939, Serial N0. 306,570

solid materials which are already granular or coarsely crushed and in particular relates to the production of nely and uniformly groundpigments.

According to the invention, the material to be pulverized is caused to pass into an apparatus such as isl hereinafter more particularly described, and an air stream is at the same time caused to flow into the apparatus, the material being then subjected to pulverlzing conditions in a conned space so arranged that the particles are acted upon by opposing forces, viz., a force applied by mechanical means of which the effect if it alone were acting would be that the particles would tend to stay in the confined space; an aerodynamic force of which the effect if it alone were acting would be that the particles would tend to be blown out of the conned space; the forces being so adjusted that material consisting of particles of different sizes is so worked on that the smaller particles are ejected from the apparatus in the issuing air stream whilstl the larger particles remain in the confined space until they are broken down and likewise are ejected.

A pulverizing Iapparatus for use according to the invention comprises (i) a cylindrical, oblate spheroidal lenticular or similarly shaped casing provided with a circular or other suitable orifice, withl its centre on or near the axis of the cylinder or spheroid, at one side; (ii) to rotate Within said casing a vane wheel comprising a hub with vanes or a disc of less diameter than the inside of the casing-fitted with vanes onthe side of the disc that faces the orifice, these vanes being fixed radially and with their planes at right angles or thereabouts to the plane of the disc, and bey ing of such area that they almost ll the outer circular space of the casing, but their inner, edges do not overlap the orifice, and the disc being also fitted with larger vanes on the other side if the stream of air through the pulverizng apparatus is to be generated wholly or partly by the rotation of said vane wheel; (iii) for introduction of the material to be pulverized into the casing one or more mouths, conveniently placed on the periphery or on the opposite side of said casing to said orice, the mouth -or mouths being so disposed that the material to be pulverized may be carried into the casing in the air stream,or may be caused to mingle with the entering air stream on arrival in the casing, and the mouth through which the air stream enters being provided with valves, dampers. blowers or the like to control, augment or separately generate said air stream as may be desired.

'I'he pulverization being accompanied by some generation of heat, the casing is conveniently fitted with an externally circumferentially arranged chamber for passing round it cooling liquid, e. g., cold water.

The orifice is advantageously fitted with an inward turning flange. v

To the orifice is connected a suitably arranged duct, leading into a suitable hopper conveniently covered by a cloth bag filter through which the issuing air, but not the pulverized material, can pass, but the invention is not limited 'to this or any other particular means of recovering the pulverized material from the issuing air.

The invention will be more particularly dethe pulverizlng apparatus; Figure 2 is a sectional elevation of another form of the apparatus; Figure 3 is asection showing a modified form ofv oriflce`1'or the casing.

Referring first to Figure 1 a is the casing and b the orifice,vc is the vane wheel rotating on shaft e, d. is a mouth, connected as shown with a pipe which provides a stream of air-with which also is carried the granular material to be pul-Y verized from the hopper h. In this form of the machine, vane-wheel c may have simple vanes almost filling the outer annular space in the casingl as shown, and mouth d is then so placed that the incoming stream of air and material to be ground will be caught by the vanes as they rotate.

Vane-wheel c is driven at about 5,000 R. P. M. 'I'he flow of air being suitably adjusted finely ground material issues in the air stream from orifice b and is caught in a suitably placed bag lter with or without a hopper as described. A coarser material whirled around by the vanes remains within the casing until it is disintegrated by impact of particle on particle, and thus the process is continuous.

Figure 2 shows a form ofthe apparatus wherein suitable vanes are provided so that the ma chine acts as its own blower. 4

Here a is the casing, with orifice b adjustable the vane wheel towards the orifice. Small vanes v1 have their inner edges approximately at right anglesto the disc in order that there beA no gen-- eration of eddy currents in the air in the annular space between the inner edges of the vanes and the projection of the circumference of the oriiice towards the disc. d2 is the mouth which acts as 4air inlet provided with a valvey or damper not shown. di with pipe attached is the mouth forl introduction of the material to be pulverized. 'lit .will be understood that these two mouths may be arranged in respect -of one another in various ways, it being only necessary that the mouth which acts as air inlet shall be so set in relation to vanes 'v2 that these when rotated suck air at the desired rate into the casing, and the material to be ground passes into the casing so that it becomes mingled with the entering air as that passes into the'annular space between the cylindrical wall of the casing and the vane wheel. Figure 3 shows a modiiied form of orifice which may be tted if desired to the apparatus of Figl ure 2.

Thus, in a particular form of the apparatus according to Figure 2, the casing was a cylinder.

of 181/29" internal diameter and 8 in depth from mouth to orifice, the air inlet mouth was approx'- imately 2 sq. in. The oriiice was'l2 in diameter. The vane wheel, provided lwith varies as shown in Figure 2, was driven at'3,200 R. P. M. Then a turkey red iron oxide was passed through at such a rate that there was nochoking. In this way the issuing pulverized material was collected asuman at the rate of 56 lbs. per hour showing only 0.34% retained on a No. 240 B. S. S.'sieve. This pigment was of much better'quality than that obtained by `grinding the same raw material in a mili of the kind usually used for such purposes,

being brighter in the dry state and brighterV in4 shade when used as a paint in linseed oil, andy having greater colour value.

We claim: y

A puiverizing apparatus comprising in combination a cylindrical-shaped casing provided with an adjustable circular discharge orifice arranged substantially coaxial with a rotor element vmounted for rotation within said casing, said rocurrents in the air in the annular spaces between their inner edges and the projection o1' the circumference of the orifice towards the face of said, rotor. and an inlet for introducing material into said casing to be subjected to the pulverizing 30 action of said rotor.

'mEVOR A. sii/frm; RONALD HOLLOWAY THOMPSON. 

